This section provides background information related to the present disclosure which is not necessarily prior art.
In the following description and the accompanying claims, the expression “closure device” will be used to generally indicate any element movable between an open position and a shut position, respectively opening and closing an access to an inner compartment of a motor vehicle, therefore including, boot, rear hatches, bonnet lid or other closed compartments, window regulators, sunroofs, in addition to the side doors of a motor vehicle, to which the following description will make explicit reference, purely by way of example.
It is known that electrical latches are provided in motor vehicles, for example for controlling opening and closing of the side doors.
An electrical door latch generally includes a latch mechanism having a ratchet that is selectively rotatable with respect to a striker fixed to a door post in order to latch and unlatch the door. The latch mechanism also includes a pawl that selectively engages the ratchet to prevent the ratchet from rotating. The electrical door latch includes an electric motor, which is electrically connected to a main electric power supply of the vehicle (for example to the 12V battery of the same vehicle), in order to directly or indirectly drive the pawl, via an electrically-operated latch release actuator.
As it is known, a common problem related to electrical latches is that of controlling, as it is also required by security regulations, the opening and closing of the doors even in case of failure of the main power supply of the vehicle, or in case of interruptions or breaking of the electrical connection between the main power supply and the electric motor in the latch; this kind of situation may occur for example in case of an accident or crash involving the vehicle.
Additionally, the use of electrical door latches leads to the use of door handle switches or sensors to determine, for example, the position of the handle or handle activation (i.e., has the handle been pulled or not). These handle switches may connect to control circuitry or control units associated with the electronic latch via a wired connection. However, such door switches can experience failures and/or wiring connected to the switches may fail or become shorted to ground, or to other wires, such as wires carrying vehicle battery voltage. Failures associated with the handle switch and/or associated wiring can, for example, can trap occupants of the vehicle (e.g., door handle movement is not properly detected) and/or lead to spontaneous release of the electronic latch or door opening (e.g., the switch state is erroneously read due to an issue in the wiring to the door handle switch). Known solutions for diagnosing door switch issues are generally incapable of detecting all possible dangerous failure modes and/or utilize complicated detection schemes.
A need therefore exists in the field for an improved circuit for operating a handle switch and diagnostics of the handle switch and a method of operating the circuit.